Glycopyrrolate (also known as glycopyrronium bromide) is a bromide salt with a quaternary ammonium counterion with the chemical name of 3-[cyclopentyl (hydroxy)phenylacetoxy]-1,1-dimethyl pyrrolidinium bromide, a molecular formula of C19H28BrNO3 and a molecular weight of 398.34. Its chemical structure is shown in Table 2 below.
Trospium chloride is a quaternary ammonium salt with the chemical name of 3 (2 hydroxy-2,2 diphenylacetoxy)spiro[bicyclo[3.2.1]octane-8,1′pyrrolidin]-1′-ium chloride. The molecular formula of trospium chloride is C25H30ClNO3 and its molecular weight is 427.97. The chemical structure of trospium chloride is:

The quaternary ammonium antimuscarinic drugs (QAAM) are particularly useful because of their ability to antagonize endogenous acetylcholine during periods of excessive acetylcholine production, or prolonged acetylcholine effect from physiologic and pharmacologic reasons. These compounds share the property that they do not appreciably penetrate the central nervous system (CNS), and glycopyrrolate and trospium chloride have been particularly useful in treating patients in need of a peripheral anticholinergic effect on antimuscarinic receptors.
The same biochemical property that is advantageous in preventing CNS distribution, also limits intestinal absorption, requiring the currently available formulations of these medications to be taken in the absence of food, and resulting in incomplete and variable bioavailability in patients.